Action
Notice of proposed rulemaking (NPRM).
Summary
The FAA proposes to supersede Airworthiness Directive (AD) 2021-14-20, which applies to all The Boeing Company Model 737 airplanes. AD 2021-14-20 requires repetitive functional tests of the cabin altitude pressure switches, and on-condition actions, including replacement, if necessary. AD 2021-14-20 also requires reporting test results. Since the FAA issued AD 2021-14-20, data collected from the reports required by AD 2021-14-20 revealed that the switches were subject to false test failures due to lack of clear instructions for setup of the test adapters during the functional tests. This proposed AD would retain the repetitive functional tests and on-condition actions, and specify certain adapter requirements for the functional tests. The FAA is proposing this AD to address the unsafe condition on these products.